05/08/2015
*Now this is how drawbacks or adverse effects of a system can be used as a solution to problems created by them.*
Fields covered- Antennas,
Plasma sheath,
Automated control system,
Capacitive & inductive effects,
Spacecraft.
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When hypersonic vehicles like spacecraft zips along at five or more times the speed of sound towards earth's atmosphere, an envelope of hot ionized air, called a plasma sheath, surrounds it.
This plasma sheath will reflect electromagnetic signals under most conditions, cutting off connection with anything outside of the vehicle leading to 'COMMUNICATION BLACKOUT' between earth station and spacecraft.
NOW THE IDEA:-However, under certain special conditions, a plasma sheath can actually enhance the radiation from a communication antenna.
They propose adding a "matched layer" to ordinary communication antennas to create the desired resonant conditions during normal hypersonic flight.
The matched layer works because it acts as like a capacitor -- a type of electrical energy storage unit -- in the antenna circuit, Gao explained.
The plasma sheath, on the other hand, acts like an inductor, which resists changes in an electric current passing through it. When a capacitor and an inductor are paired together, they can form a resonant circuit.
"Once the resonance is reached, the energy can be exchanged between them steadily and losslessly, like real capacitance and inductance do in a circuit," Gao said.
"As a result, the electromagnetic radiation can propagate through the matched layer and the plasma sheath like they do not exist."
Work by- Xiaotian Gao, a physicist at the Harbin Institute of Technology in China and his colleague Binhao Jiang.
http://www.sciencedaily.com/releases/2015/06/150616114053.htm
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